1. FIELD OF THE INVENTION
This invention relates to a dry analytical element suitable for assaying enzymatic activity in a liquid.
2. DESCRIPTION OF THE PRIOR ART
Dry analytical elements, especially integral multilayer dry analytical elements are known and described e.g., in U.S. Pat. No. 3,992,158 and Japanese Patent Application (OPI) No. 1643/81 (The term "OPI" as used herein means "unexamined published application"). It is disclosed in Analytical Chemistry, Vol. 55, No. 4, 498A-514A (1983) that the integral multilayer dry analytical element can be applied to the assay of enzymes in serum.
The integral multilayer dry analytical element generally comprises a liquid-spreading layer having a liquid measuring function as an uppermost layer. When a liquid of an amount V is developed in the liquid spreading layer, the developed area is proportional to V (V=ka). Since the amount of the liquid per unit area is decided by the proportionality constant k between the spreading area and the liquid amount V, the analytical sensitivity depends on the proportionality constant k. As the proportionality constant k becomes smaller, the amount of the liquid per unit area becomes greater so that the enzymatic activity per unit area becomes higher and the analytical sensitivity is increased.
An integral multilayer dry analytical element in which the porous liquid-spreading layer comprises water non-absorbent fibers is disclosed in Japanese Patent Application (OPI) Nos. 164356/80 and 222769/85. Water non-absorbent long fibers, such as polyesters, polyamides (e.g., nylon), etc., retain little water and, when woven or knitted, provide a uniform spreading layer and are, therefore, suitable for use in dry analytical elements utilizing a reaction rate method. However, such a porous liquid-spreading layer composed of water non-absorbent fibers has a large proportionality constant k so that a high analytical sensitivity cannot be assured.